1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer or a copying machine which performs image formation using electrophotographic method or the like.
2. Description of the Related Art
Japanese Patent Laid-Open No. 5-294005 discloses an image forming apparatus that scans a photosensitive member at once by a plurality of light beams using a VCSEL (Vertical Cavity Surface Emitting Laser) including a plurality of light sources to speed up image formation.
In the image forming apparatus that scans using a plurality of light beams, stripes are generated in the scan direction in which the light beams scan the photosensitive member due to the variation between the elements or the nonuniform scan line intervals. To suppress the degradation in image quality, Japanese Patent Laid-Open No. 2004-109680 discloses an image forming apparatus that performs so-called multiple exposure in which the surface of a photosensitive member is exposed a plurality of times based on the same image data.
The multiple exposure makes it possible to suppress the degradation in image quality caused when the photosensitive member is scanned by a plurality of light beams. However, since the spot position of overlaid light beams may shift, the latent image may blur, and the image sharpness may lower. This leads to degradation in quality of a character image which particularly needs to be reproduced sharply.